Centrifugal pump



Feb. 15, 1949. e. P. HOWARD ETA!- 2,461,821 '1 CENTRIFUGAL PUMP Filed Aug. 2, 1946 Patented Feb. 15, 1949 UNITED STATES PATENT OFFICE CENTRIFUGAL PUMP Giles Philip Eliot Howard and Alexander Ivanoif, Luton, England Application August 2, 1946, Serial No. 687,823 In Great Britain July 11, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires July 11, 19.65

2 Claims. (01. 1oa-103) l 2 This invention relates to centrifugal pumps, nated by the reference 2. As in said co-pending and more particularly to centrifugal pumps application the motor casing l and the pump which are intended to handle liquid at high casing 3 are embodied in one common casing, temperatures. which has a reduced neck 4 between said motor The object of the invention is the provision of 5 and pump casings, in which neck is located one improvements in such pumps, the purpose of of the journal bearings for a shaft 5 which is which is, either to reduce the temperature at cercommon to both pump and motor.

tain points of the pump, such as the stuffing box, Also, as in said co-pending application, the or to limit the maximum rate of change of temfluid within the common casing is cooled by circu perature at such points as the joint faces of the lating it, from the upper end of the motor casing pump casing which may be caused by the sudden (not shown), through a coil immersed in a coolvariation of the temperature of the pumped fluid. ing tank (not shown), and back to the common In a. centrifugal pump the liquids are customarily casing through a hole in the wall of the reduced moving at high velocities, with the result that neck 4 by way of a pipe 6. the walls and the internal parts are traversed by The impeller 2 is mounted on the lower exrapidly moving fluids. Any sudden changes in tremity of the shaft 5 and is adapted to draw the temperature of the fluid are therefore comthe fluid in coaxially through an inlet port I at municated without great delay to the surface of the lower end of the pump casing, and deliver it the metal comprising such walls or internal parts, radially through an outlet port 8 in the plane of and such sudden changes result in violent thersaid impeller. Between said impeller and said mal stresses. outlet port 8 is provided a diffuser 9. This is In accordance with the present invention a the subject of our co-pending application Serial series of heat bafllesis provided, the purpose of No. 687,824, filed of even date herewith, now mawhich is to create between the baffles and the tured into Patent No. 2,450,143 of Sept. 28, 1948 walls or between several baf'fles a single layer or and will not be further described herein. multiple layers of stagnant liquid. The heat In accordance with the present construction transfer through such layers would be largely by the back cavity H! of the pump casing 3, i. e. the conduction and natural convection and would cavity on the side of the pump impeller 2 remote therefore be considerably reduced in magnitude from the inlet conduit 1, is made cylindrical and as compared with the forced convection which larger, both as to its diameter and its axial exwould result were the baffles not present. t. than t at Shown n our t -p pp The invention may be suitably applied to the tion aforesaid. Also the journal bearing for the pumps of pump-motor combinations, as described shaft 5 is set back further from the pump miand claimed in the co-pending application of peller 2 so as to be clear of the said back cavity Alexander Ivanofl, Serial No. 792,013, filed Dec. III. In this cylindrical back cavity ID are located 16, 1947, in which the pump pumps fluid at high a plurality of disc-shaped baiiles II coaxially temperature and pressure .and the motor casing, round the shaft 5.

which is in effect a part or extension of the pump The said back cavity In is in communication, casing, contains fluid whose pressure is of the in the usual way, by way of holes l2 through the same order as the pressure of the fluid being pump impeller, with the pump input, and is therepumped. fore filled with fluid, and, in the ordinary way, In order that the invention may be the more the temperature of this fluid owing to forced clearly understood a centrifugal pump structure convection, would rapidly approximate, throughin accordance therewith will now be described, out said back cavity, that of the fluid being reference being made to the accompanying drawpumped, and thus, if 'for example the fluid being me which is a sectional side elevation of said pump w r o ri e o a hi h p rat r the pump structure. fluid in the back cavity would rapidly transfer Referring to this drawing, the pump structure the same temperature to, for example, the journal therein illustrated is associated in one assembly bearing. with a driving electric motor, in the same gen- When bailles II as above described are emeral way as in the co-pending application Serial ployed, however, a plurality of layers of substan- No. 792,013 aforesaid. In the present drawing tially stagnant liquid are produced between the the whole of the motor is omitted save for the several baflles, and between the end baille and the near end of the motor casing which is designated end of the back cavity, and the rate of heat by the reference I. The pump impeller is desigtransfer through these several layers, which can only be by conduction and natural convection, will bee-much less than that caused by the forced convection if the baffles were not present. Thus the journal, for example, will remain at a considerably lower temperature.

The baffles ll may be mounted, at their inner edges, on a fixed sleeve l3 closely surrounding the shaft 5 and at their outer edges they may be touching the inner periphery of said back cavity. The sleeve l3 at its end remote from the pump may be formed with a flange l4 whereby it is attached to the back wall of the pump casing. For giving increased rigidity to the bafiies II a number of posts are provided which are mounted at their upper ends to the back wall of the pump casing and which extend downwardly through holes in said baffles, suitable spacing washers being mounted on said posts 15 between said baffles.

As the metal of the bailies ll does not, in any case, offer great resistance to the passage of heat it is intended that said baffles should be made of comparatively thin gauge metal and that the sleeve l3 carrying them should only be strong enough to resist the forces due to impact of the moving liquid. It will be seen that, provided it is ensured that the layers of liquid are substantially stagnant as stated, there is no need to ensure a hermetic seal between the baffles and the adjacent parts.

In the particular example of the invention above described the main purpose of the baffles II is to ensure that should the aforedescribed cooling circulation, by way of the cold coil and the pipe 6, fail, owing for example to stoppage of the motor through a failure of the electric current there would be no violent flow of heat, from the body of the liquid inside the pump casing, or from the metal comprising the pump shell, towards the electric motor.

As shown, the pump casing 3 consists of two portions 3a and 3b having annular junction faces at IS in a plane transverse to the shaft 5. It is a further specific purpose of this particular example of the invention to limit the maximum rate of change of temperature at the region of these junction faces. The said cylindrical back cavity ID in which the baffles l l are located is constituted by a cylindrical recess in the back or upper portion 3a of the pump casing 3, that is the portion which carries the stuffing box. The outer surface I! of this portion 3a is also made cylindrical over most of the length of said back cavity. The front or lower portion 31) of the pump casing, in which the inlet and outlet are formed, has a rear annular extension l8 which surrounds the said outer cylindrical surface I! of the portion 3a, and the surface at the rear end of this extension [8 abuts against the front surface of an annular enlargement or flange I9 formed on said portion 3a, and the two portions are bolted together by means of bolts at these tvvo abutting surfaces, which thus constitute the said junction faces of the pump casing. Owing to the baffles H the rate of heat flow from inside the back cavity to the junction face on the portion 3a of the casing is much rutricted. The rate of heat flow to the junction face on the portion 3b of the casing, which depends on conductivity through the substantial thickness of the aforesaid rear extension I8, is also relatively low. The heat flow to the region of the junction is therefore fairly slow and the temperature of the junction faces rises and falls slowly, thus giving the junction faces a chance to attain the same temperature, by radiation and conduction from one side of the junction to the other. The arrangement has the additional desirable feature that the reduction of the rate of change of temperature of the junction also minimises the difference of temperature between the aforesaid flanges I9 on the portion 3a of the casing and the bolts 20 passing through said flange. These bolts 20, being surrounded by a thin layer of air, which it is almost impossible to avoid, are generally slower in responding to temperature changes because they have to receive their heat either axially from that part which is screwed into the metal or by radiation and convection across the air layer. Either of these processes is somewhat slow. If the temperature of the flange 19 drops rapidly, the temperature of the bolts 20 drops considerably more slowly, with the result that the bolts become longer in relation to the thickness of the flange, and this reduces the clamping pressure holding the junction tight. The present construction, in reducing the rate of change of heat at the region of the junction faces, increases the tendency of the bolts 20 to be at the same temperature as the two parts of metal which they bolt together, and therefore enables the junction to remain tight and unchanged throughout.

Further constructional details are in the main sufficiently clear from the drawing. It will be seen that the shaft 5 for some distance from its lower end is made hollow, the impeller 2 being mounted on a plug element which is, say, welded in the open lower end of said shaft. By making the shaft hollow in this way the rate of heat transfer from the pump towards the motor is still further reduced.

It will also be seen that the external surface of the reduced neck 4 is formed with annular vanes 2|. This increases the surface radiation of heat from said neck portion and still further reduces the transfer of heat from the pump towards the motor.

In the particular construction being described, a tilting-pad type of bearing is employed for the shaft 5. The reference 22 designates the tilting pads. The bearing surfaces of these pads engage around a sleeve 23 which is fast on the shaft 5 and they make tilting engagement with a surrounding sleeve member 24 which forms a lining within the reduced neck 4. As in prior British Patent No. 553,443 the member 24 has a conical inner surface with which the pads 22 engage, and a. cage element 25 screwed into said member 24 draws the pads against said conical surface.

As will be clear from the drawing the member 24 has an end flange whereby it is secured to the back wall of the pump casing by the same bolts which secure the sleeve I3.

We claim:

1. A centrifugal pump comprising a. pump impeller, a pump shaft on which said pump impeller is mounted, said pump shaft extending rearwardly from said pump impel] ump Wimp impeller having a fluid inLet..and----outlet, said pump casing being provided with a back cavity at the rear of said pump impeller, through which back cavity said shaft passes in contact with the fluid in said back cavity, said back cavity being in free communication with the fluid inlet aforesaidgeansJon ance between said shaft and said baflles, and stationary means surrounding said shaft and sealing theEpaces between said baffles at the region of the edges of their holes, said stationary means defining a fluid cut-off between said bafiies and said shaft, and prelq ting the generation of motion in the fluid between said bafiles by the rotation of said shaft.

2. A centrifugal pump as defined in claim 1, wherein said bafiles at their outer edges substantially touch the inner periphery of said back cavity.

GILES PHILIP ELIOT HOWARD. ALEXANDER IVANOFF.

REFERENCES CITED 1 The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,736,002 Frickey et a1. Nov. 19, 1929 1,773,909 Korb Aug. 26, 1930 [0 1,882,519 Pfefier Oct. 11, 1932 2,239,228 Hankison Apr. 22, 1941 

